This invention generally pertains to systems and manifolds for delivering chemicals from bulk delivery canisters to manufacturing process tools such as chemical vapor deposition (CVD) devices, and more particularly for process tools utilized in the fabrication of integrated circuits.
The production of electronic devices such as integrated circuits is well known. In certain steps in such production, chemical may be fed to certain process tools which use the chemical. For instance, a CVD reactor is commonly employed to generate a layer of a given material, such as a dielectric or conductive layer. Historically, the process chemicals were fed to the CVD reactor via bulk delivery cabinets. The chemicals used in the fabrication of integrated circuits must have a ultrahigh purity to allow satisfactory process yields. As integrated circuits have decreased in size, there has been a directly proportional increase in the need for maintaining the purity of source chemicals. This is because contaminants are more likely to deleteriously affect the electrical properties of integrated circuits as line spacing and interlayer dielectric thickness decrease. The increasing chemical purity demands also impact the chemical delivery systems.
Thus, there exists a need for improved chemical delivery systems such that impurities are not introduced into the process tools during chemical canister replacement or refilling procedures, and other maintenance procedures. The impurities of concern may include particles, moisture, trace metals, etc. In order to meet these more demanding requirements, improved manifold systems are required.
Further as chemical purity demands have increased, the variety of chemicals utilized in integrated circuit manufacturing have increased. Moreover, some of the chemicals being contemplated for integrated circuit manufacturing exhibit more demanding physical properties and/or are more toxic than previous chemicals utilized, thus placing additional demands upon the chemical delivery system. For example, very low vapor pressure chemicals having a vapor pressure of less than 100 mT and even less than 10 mT are contemplated for use in integrated circuit manufacturing. One such chemical, TaEth (tantalum pentaethoxide) has a vapor pressure of less than 1 mT and is contemplated for use in the CVD formation of dielectric layers. Another such chemical, TDEAT (tetrakis(diethylamido)titanium) has a vapor pressure of approximately 7 mT and is contemplated for use in the CVD formation of titanium nitride layers. Yet another low vapor pressure chemical is TEASate (triethyl arsenate). Additional low vapor pressure chemicals may be those utilized to deposit conductor layers formed of copper or TaN. Because the vapor pressures of such chemicals are so low, traditional methods of purging the manifold system of a chemical delivery system are inadequate. While existing manifolds adequately allow traditional compounds to be removed from the lines and manifold through repeated vacuum/gas purge cycles, such vacuum/gas purge cycles may not adequately remove very low vapor pressure materials. Thus, a need exists for an improved method and apparatus for purging a manifold system such that very low vapor pressure chemicals may be adequately purged from the various components of the chemical delivery system. Further, materials such as TaEth may require heating of the chemical cabinet. It is thus desirable to have a chemical delivery system which efficiently incorporates a heating system into the gas cabinet.
Other chemicals also place increased demands upon the purging techniques utilized. For example, chemicals which include solid compounds in solution with a liquid may also be used as reactants in the manufacture of integrated circuits. The solid compounds are typically stored in chemical canisters as dispersions in an organic liquid. For example, solid reactants such as barium/strontium/titanate (BST) cocktails (solutions) utilized for forming dielectric layers may be dispersed in a liquid such as tetrahydrofuran (THF) or triglyme. A wide variety of other solid materials may also be used in conjunction with other organic liquids, such as for example as described in U.S. Pat. No. 5,820,664 the disclosure of which is incorporated herein by reference.
When such solid compositions are sold and used in canisters, the canisters are often adapted such that they may be connected to a manifold for distribution of the chemical, such as described in U.S. Pat. Nos. 5,465,766; 5,562,132; and 5,607,002. However, when the canister is changed, existing manifolds do not adequately accommodate the ability to clean out the manifold and lines prior to change out. Thus, if a vacuum/gas purge cycle is used with a solid/liquid composition, the liquid will be evaporated away to leave solid compounds in the lines. This is unacceptable, especially if the canister is being changed out to another compound since the line is contaminated. Particle contamination and chemical concentration variation may cause severe process problems at the process tool. A solution to this problem would be highly desirable.
Further, it is desirable to improve the clean out and purge processes because the chemicals utilized may be highly toxic, noxious, etc. Thus, it is desirable to reduce the residual levels of low vapor pressure chemicals (such as discussed herein) within the manifold and lines of the chemical delivery system.
Moreover, at least some of the chemicals contemplated for use in deposition systems have ambient temperature requirements which may require elevated temperatures to prevent solidification. Thus, a chemical delivery system which addresses the above described problems while efficiently and economically providing a controlled temperature environment is desirable.